Study On Preparation And Properties Of Salicylaldehyde Schiff Base Thermochromic Materials

Salicylaldehyde Schiff base is a kind of materials with excellent thermochromic properties.In this paper,salicylaldehyde bis-Schiff bases(BSPs)with four different substituents were synthesized by the reaction between salicylaldehyde derivatives and p-phenylenediamine.One of the products which was O-vanillin-p-phenylenediamine Schiff base(BSP2)was selected as a ligand to coordinate with Cu and Ni ions and their corresponding complexes were synthesized by solution.Finally,three kinds of salicylaldehyde Schiff bases with better thermochromic properties were used as fillers,and Acrylic(AAS)and epoxy(EP)were used as binders to prepare six thermochromic coatings.And through the characterization of the structure and the performance test,the discoloration mechanism of salicylaldehyde Schiff base was confirmed,and the discoloration difference between salicylaldehyde Schiff base and salicylaldehyde Schiff base metal complex was compared.The salicylaldehyde Schiff base can be sprayed as a coating as a thermochromic filler.Following parts are included:(1): Four kinds of BSPs samples were synthesized by salicylaldehyde,o-vanillin,4-methoxy salicylaldehyde and 5-nitrosalicylaldehyde and p-phenylenediamine respectively.BSP2 is used as a ligand to coordinate with Cu and Ni ions,and two metal complexes were synthesized.The samples were characterized by HNMR,FTIR,UV and EDS spectroscopy and the related results have proven that the composition of the products were the target BSPs and metal complex.The thermochromic properties of the BSPs were investigated and analyzed by TG-DSC,thermochromic and infrared emissivity testing.(2): The test results show that BSPs can perform reversible thermochromism.In addition,BSP1 has the shortest response time(10s)and best cycle stability ΔE2(2.6),while BSP1 has the lowest infrared emissivity(0.73)at 8~14μm.Therefore,BSP1 is a good thermochromic material.However,the discoloration types of BSP2-Cu and BSP2-Ni belong to irreversible thermochromism,and the metal complexs is green.The ΔE1 of BSP2-Cu or BSP2-Ni is much larger than BSP2,and the thermochromism properties are more excellent,while BSP2-Cu has the lowest emissivity(0.67)at 8-14μm.(3): Three BSPs thermochromic fillers with excellent discoloration properties were combined with AAS and EP adhesives to prepare six thermochromic coatings.The thermochromic properties and infrared emissivity were tested.The results show that the thermochromic properties of the coating are not affected after the BSPs fillers to form coatings.However,whether it is at 3~5 μm or 8~14 μm,the emissivity of the coating is higher than the emissivity of the filler.Combined with emissivity and thermochromism,EP is more suitable as a binder to form a thermochromic coating with salicylaldehyde Schiff base fillers.